Torsional vibration dampers are employed with engines utilizing crankshafts to absorb and damp vibrations occurring within the crankshaft. Such dampers are normally mounted exteriorly of the engine block on the end of the crankshaft, and may include pulley components for driving alternators, power steering pumps, air conditioners, and other accessory equipment.
The basic torsional vibration damper includes a hub member directly mounted upon the crankshaft, an elastomer mounted on the hub member, and an inertia member mounted on the elastomer. Vibrations existing within the hub member are transferred to the inertia member through the elastomer, and the radial separation of the inertia member from the axis of rotation, and its mass, damp vibrations within the hub member and crankshaft. The energy produced by the damping action causes the elastomer to heat due to its internal movement and stress, and this heat is dissipated through the hub and inertia members.
The elevated temperatures which may occur in heavy duty vibration dampers can reach such values as to deterioriate and destroy the elastomer, and it is known to utilize cooling means with torsional vibration dampers to minimize deleterious thermal problems. Such cooling devices may include fins, such as shown in U.S. Pat. No. 3,314,304, or may include passages and openings through which air passes as the damper rotates, such as shown in U.S. Pat. Nos. 2,594,555; 2,716,904; 2,779,210; 3,443,454 and 3,678,708. While such prior dampers utilizing air passages do tend to reduce the damper operating temperatures, such prior devices have not achieved heat dissipation characteristics totally acceptable with heavy duty vibration dampers as employed with truck and industrial engines.
It is an object of the invention to provide a torsional vibration damper capable of absorbing heavy vibrations and dissipating the heat generated within the damper wherein a long operative life of the elastomer is achieved.
A further object of the invention is to provide a torsional air cooled vibration damper employing a composite inertia ring wherein a metal ring of high thermal conductivity is utilized in direct engagement with the elastomer, and a high density metal ring is mounted upon the thermal conducting ring, and air passages are defined in one of the rings adjacent the mating surfaces thereof for the effective dissipation of heat transferred to the inertia ring by the elastomer.
A further object of the invention is to provide a torsional air cooled vibration damper utilizing cooling air passages having both axial and radial portions, wherein the air passages are economically and accurately formed, and wherein air flow therethrough is effectively achieved.
A hub member is attached to the crankshaft to be damped, and the hub member includes a cylindrical peripheral surface upon which an elastomer is mounted. An annular inertia ring having an inner cylindrical surface is mounted upon the elastomer, and in practice, the elastomer may be inserted intermediate the hub and inertia ring surfaces under tension in the manner described in the assignee's U.S. Pat. No. 3,280,654. The inertia ring includes a first annular inertia member formed of a metal having a high rate of thermal conductivity, such as aluminum, and this inner member directly engages the elastomer in heat transfer relationship thereto. The first inertia member includes a cylindrical surface concentric with the axis of rotation, and also includes a radial shoulder surface defined upon a radial projection formed on the first member.
A second inertia member of annular configuration is firmly and intimately mounted upon the first member cylindrical surface, such as by an inteference fit, and the second member engages both the cylindrical and shoulder surfaces of the first member. A plurality of air passages are defined in the second member adjacent the surfaces thereof which engage the first member wherein air flowing through the air passages passes over exposed surfaces of the heat conductive first member dissipating the heat transferred thereto by the elastomer.
The second member is preferably formed of a relatively high density metal such as steel or cast iron, and the air passages preferably includes both axial and radially extending portions jointed at an intersection having a radius surface to aid in air flow. The air passages intersect the periphery of the inertia member, and air passages may be randomly spaced about the axis of rotation to control audible vibrations which may be produced thereby.